[Influencing Factors of Bacterial Activity in Water Distribution Networks]

In order to study the variation patterns of bacterial activity in water distributed networks, this paper studied a simulated water distribution network in a northern China city. Microscopic examination and bacterial counts were conducted on acridine orange-stained bacteria using fluorenscence microscopy to ensure precise quantitative analysis. The ratio of viable bacterial count to total bacterial count was used to characterize the overall bacterial activity in the drinking water distribution network,as well as to study the impacts imposed by various factors. As indicated, this method was proved to be rapid,reliable and repeatable in bacterial counts. Populations of viable bacteria and total bacteria in water samples were 10³-10⁴ cells·mL^-1 and 10⁴-10⁵ cells·mL^-1, respectively. There was a positive correlation between the bacterial activity and water temperature, turbidity, and flow velocity. There was also a negative correlation between bacterial activity and residual chlorine after the operation stabilized. The capacity of different forms of bacteria in the simulated water distribution networks with tolerance of sodium hypochlorite was in the following order:long-rod-shaped, spherical-shaped, short-rod-shaped, and curved-shaped. The reactivation and reproduction capability of rod-shaped bacteria was stronger. There were more short-rod-shaped bacteria in summer water samples than in winter.